In semiconductor manufacturing, a process corner is an example of a design-of-experiments technique that refers to a variation of fabrication parameters used in applying an integrated circuit design to a semiconductor wafer. Corners analysis provides a convenient way to measure circuit performance while simulating a circuit with sets of fabrication parameter values that represent the most extreme variations in a manufacturing process. In a manufacturing process, process variables can theoretically have exact values and these exact values can be used to calculate the yield for the process. However, in a real manufacturing process, process variables are subject to a manufacturing tolerance and can fluctuate randomly around their ideal values. In addition, the circuit is expected to operate in different environment conditions, such as low and high temperature. The combined process and environment variation for all of the components results in an uncertain yield for the circuit as a whole. Corners analysis looks at the performance outcomes generated from the most extreme variations expected (the corners), such as variations in the manufacturing process, operating voltage, and temperature of the circuit. Based on this information, it can be determined whether the circuit performance specifications can be met, even when the process and environment variations combine in their most unfavorable patterns.
Corner analysis modules can be included in electronic design automation (EDA) software to perform corner analysis of an integrated circuit (IC) design. Designers often need to design against a large number of corner combinations (e.g., supply voltage (Vdd), input slew rate, output load, bias current, temperature, transistor model sections, and the like). For a particular design, there typically exist few worst case corners for which the performance is worse than all other corners. Accordingly, simulation time can be significantly saved by designing only against these corners.
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